An OLED display product manufactured by the ink-jet printing method has advantages of increased material utilization and shortened manufacturing period. Therefore, more and more manufacturers use the ink-jet printing method to manufacture the OLED display products.
The ink-jet printing for the OLED display product requires an accuracy of one pixel. Thus, during the ink-jet printing, a relatively high accuracy of ink droplet for printing may be required. In the meanwhile, for accurately controlling a thickness of printed film, it is also necessary to accurately control ink volume printed into each pixel.
In an ink-jet printing device, a printing head is the most essential part. Usually, a plurality of nozzles may be provided on the printing head. The plurality of nozzles may be arranged in one or more rows. At the time of printing, a certain film layer on the OLED display substrate can be printed by translating the printing head.
Usually, since the nozzles provided on the printing head have the same specification and size, the same volume of ink droplet can be discharged from the nozzles. Further, the volume of ink droplet discharged from the nozzles can only slightly fluctuate around a fixed value. Therefore, in the practical printing, a total volume of ink droplet discharged from the nozzles can only be substantial integral multiples of the fixed value. As a result, the thickness of the film layer formed on the OLED display substrate cannot be flexibly adjusted, such that the thickness of the film layer formed by printing cannot be accurately controlled, finally influencing the display performance of an OLED display product.